Abstract: In order to investigate the current status of epilithic algal communities in the main stem of Hanjiang River and to conduct a health assessment on the aquatic ecosystem in Hanjiang River watershed, based on the sampling data from May 2023 (spring) and November 2024 (autumn) in the main stem of Hanjiang River, this study uses Redundancy analysis (RDA) to analyze the structural characteristics of epilithic algal communities. The Periphyton Index of Biotic Integrity (P-IBI) is applied for river health assessment, and Pearson correlation analysis is utilized to identify the relevant environmental factors affecting river health. The results showed that: ① a total of 159 species of periphyton were collected, among which 98 species belonged to the Bacillariophyta, accounting for 61. 64% of the total. ② The main impact factors for the spring algal community were TP, TN, COD, and EC, while the main impact factors in autumn were TN, pH, and flow velocity. ③ The average P-IBI score for the Hanjiang River watershed in spring was 3.923, a moderate health level, while in autumn it was 5.679, a good health level. ④ The P-IBI values in spring showed a highly significant positive correlation with TN, a significant negative correlation with EC, and significant positive correlations with pH and flow velocity. The IBI values in autumn showed a significant positive correlation with flow velocity. ⑤ The health status was better in the upper reaches of the Hanjiang River compared to the mid-to-lower reaches, with a significant difference observed between the two regions.